by Liz Szabo, USA TODAY

by Liz Szabo, USA TODAY

Colon cancer rates have fallen by 30% over the past decade in people over age 50, and colonoscopies are getting much of the credit, according to a report released Monday.

"This is one of the great public health success stories of the decade," says Richard Wender, chief cancer control officer at the American Cancer Society, whose researchers wrote the report, published Monday in CA: A Cancer Journal for Clinicians.

Doctors recommend that people at average risk begin getting screened for colon cancer at age 50.

Screening rates have climbed in recent years. The number of Americans ages 50 to 64 who have had a colonoscopy - which allow doctors to detect and remove polyps before they turn malignant - has nearly tripled, growing from 19% in 2000 to 55% in 2010. Use of colonoscopy also rose among those age 65 and over, growing from 55% in 2000 to 64% in 2010, according to the new report. To further reduce colon cancer cases and deaths, the American Cancer Society has set a goal of screening 80% of eligible people by 2018.

Colorectal cancer is the third leading cause of cancer death in the USA. The cancer society estimates that 136,830 Americans will be diagnosed with the disease this year and that 50,310 will die from it.

"We hope that we get the number much closer to zero by getting the at-risk population access to colorectal cancer screening," says Arun Swaminath, a gastroenterologist and director of inflammatory bowel disease at New York's Lenox Hill Hospital, who wasn't involved in the new study.

Death rates from colon cancer also have fallen, declining at a rate of about 3% a year over the past decade, the report found. Colonoscopies can reduce mortality by allowing doctors to find tumors when they're smaller and more curable.

"It's really reassuring that we are making progress," says Charles Fuchs, chief of gastrointestinal oncology at Boston's Dana-Farber Cancer Institute, who wasn't involved in the new study.

The biggest declines in colon cancer incidence were in people over age 65, who qualify for Medicare, which makes colon cancer screenings available for free. Those who have other forms of insurance also can get free colon cancer screenings and other preventive services, due to the Affordable Care Act.

Declines in colon cancer rates became more dramatic in more recent years, falling at an annual rate of 7.2% a year from 2008 to 2010.

Falling rates of colon cancer in older Americans are particularly striking considering that rates of the disease are actually rising slightly in younger people, most likely due to obesity and poor diet, the report says. Colon cancer rates increased by about 1.1% a year in Americans younger than 50. Authors noted that the types of colon cancers found in people under 50 were often those linked to obesity.

About 70% of colorectal cancers are related to lifestyle issues, such as obesity, lack of exercise and eating a lot of red or processed meat, Fuchs says.

"Beyond telling people to get a colonoscopy, we need to counsel people to eat a balanced diet and exercise," Fuchs says.

Americans aren't benefiting equally, Fuchs says. While colon cancer incidence dropped among all racial groups, the declines were higher in whites than among minorities. And death rates from the disease were 50% higher among blacks than whites, probably because blacks often have less access to healthcare than whites, he says.